A novel process for preparing a 1,4 benzodioxane derivative shown by the formula (1) which is a useful intermediate of circulatory drugs and drugs for psychoneurosis, characterized in sulfonating a phenoxypropanediol with a sulfonyl halide, eliminating the protective group, and then cyclizing the sulfonated compound by treating with a base followed by, if necessary, further sulfonation. ##STR1## In the above formula, R1 is H, RSO2, R is alkyl, phenyl which may be substituted with alkyl, R2, R3, R4 are H, halogen, OH, nitro, cyano, formyl, COOH, alkoxycarbonyloxy, alkyl, alkoxy, haloalkyl, N,N-dialkylamino, alkylcarbonyl, alkoxycarbonyl, phenyl which may be substituted by alkyl, etc.22
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1. A process for preparing a 1,4-benzodioxane derivative as shown by the following formula (1) ##STR7## wherein R1 is hydrogen atom or RSO2 in which R is C1 -C4 alkyl, or phenyl which may be substituted by C1 -C4 alkyl, R2, R3 and R4 are respectively hydrogen, halogen, hydroxy, nitro, cyano, formyl, carboxyl, alkoxycarbonyloxy having 1-4 carbon atoms in the alkyl portion, C1 -C4 alkyl, C1 -C4 alkoxy, C1 -C4 haloalkyl, N,N-di C1 -C4 alkylamino, alkylcarbonyl having 1-4 carbon atoms in the alkyl portion, alkoxycarbonyl having 1-4 carbon atoms in the alkyl portion or phenyl which may be substituted by C1 -C4 alkyl, or two groups among R2, R3, and R4 may be combined together to constitute methylenedioxy on adjacent carbon atoms, or two groups among R2, R3 and R4 may be combined together to constitute phenyl on adjacent carbon atoms, wherein a diol compound as shown by the following formula (2) ##STR8## wherein R2, R3 and R4 are same as defined above, R5 is benzyl, allyl, o-nitrobenzyl, t-butyldimethylsilyl or benzyloxycarbonyl, or R5 may be constituted methylenedioxy, isopropylidenedioxy, cyclohexylidenedioxy or diphenylmethylenedioxy together with oxygen atom in the hydroxy or the R5 O-group, provided that when any one of R2, R3 and R4 is hydroxy and the hydroxy is bound on the carbon atom adjacent to the carbon atom substituted by R5 O-group, is reacted with a sulfonyl halide in the presence of a base to obtain a sulfonated compound as shown by the following formulae (3) and/or (4) ##STR9## wherein R, R1, R2, R3, R4, and R5 are the same as defined above, and after elimination of the protective group R5 of the sulfonated compound, the compound is cyclized by treating with a base.
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3. The process for preparing a 1,4-benzodioxane derivative claimed in
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5. The process for preparing a 1,4-benzodioxane derivative claimed in
6. The process for preparing a 1,4-benzodioxane derivative claimed in
7. The process for preparing a 1,4-benzodioxane derivative claimed in
8. The process for preparing an optically active 1,4-benzodioxane derivative claimed in
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The present invention relates to a process for the preparation of a 1,4-benzodioxane derivative useful for the intermediate of circulatory drugs and drugs for psychoneurosis which are alpha and beta-adrenergic antagonists.
A 1,4-benzodioxane derivative is used for an intermediate for the preparation of circulatory drugs and drugs for psychoneurosis having alpha and beta-adrenergic antagonist-activity and its various kind of processes are known. For example, a method of reacting a catechol derivative with glycidyl tosylate in the presence of sodium hydride (Japanese patent publication No.9613/1994) or a method of reacting a catechol derivative with epichlorohydrin in the presence of pyridine (J. Org. Chem. 46,3846 (1981)) is known. A method is also known to make a 1,4-benzodioxane skeleton by reactng a catechol derivative with glycerol 1-tosylate acetonide and, after removing the protective group, the acetonide, by introducing two tosyl groups onto it and then by isolating it, and further by cyclizing it (J. Chem. Soc., Chem. Commun., 921 (1976)).
Among the above methods, besides the method comprising the use of glycidyl tosylate is costly because of expense of that compound, the epoxy group is also reduced on the deprotection by hydrogenolysis and the yield decreases. In the method comprising the use of epichlorohydrin, the excess of epichlorohydrin and dichloropropanediol as a by-product must be eliminated by their evaporation with xylene, and the hydrochloric acid and acetic acid used must be eliminated by evaporation with ethanol, and therefore such procedures are troublesome. Moreover, the reaction is carried out under reflux of piperidine or hydrochloric acid. Therefore a compound having substituents which are unstable to an acid or a base can not be used. When using a optically active epichlorohydrin, racemization occurs and an optically pure product cannot be obtained. In the method which comprises the reaction of a catechol derivative with glycerol 1-tosylate acetonide, the resulting ditosylated product must be separated after tosylation and therefore the yield of the ditosylated product is 55%, or lower. These methods have many disadvantages in application of an industrial scale. An improved method has been desired.
The present inventors, taking into consideration the above fact, extensively engaged in study to find an improved method for the preparation of a 1,4-benzodioxane derivative, and found the present invention. After sulfonating a phenoxypropanediol compound, by cyclizing the resulting product in the presence of a base, the desired 1,4-benzodioxane derivative is favorably obtained in an industrial scale.
The present invention relates to a process of preparing a 1,4-benzodioxane derivative as shown by the following formula (1) ##STR2## wherein R1 is a hydrogen atom or RSO2 in which R is C1 -C4 alkyl, or phenyl which may be substituted by C1 -C4 alkyl, R2, R3 and R4 are, respectively, hydrogen, halogen, hydroxy, nitro, cyano, formyl, carboxyl, alkoxycarbonyloxy having 1-4 carbon atoms in the alkyl portion, C1 -C4 alkyl, C1 -C4 alkoxy, C1 -C4 haloalkyl, N,N-di C1 -C4 alkylamino, alkylcarbonyl having 1-4 carbon atoms in the alkyl portion, alkoxycarbonyl having 1-4 carbon atoms in the alkyl portion or phenyl which may be substituted by C1 -C4 alkyl, or two groups among R2, R3, and R4 may be combined together to constitute methylenedioxy on adjacent carbon atoms, or two groups among R2, R3 and R4 may be combined together to constitute phenyl on the adjacent carbon atoms, which is characterized in reacting a diol compound as shown by the following formula (2) ##STR3## wherein R2, R3 and R4 are the same as defined above, R5 is benzyl, allyl (e.g. 2-propenyl, etc.), o-nitrobenzyl, t-butyldimethylsilyl or benzyloxycarbonyl, or R5 may be constituted methylenedioxy, isopropylidenedioxy, cyclohexylidenedioxy or diphenylmethylenedioxy together with oxygen atom in the hydroxy or the R5 O-group, provided that when any one of R2, R3 and R4 is hydroxy and the hydroxy is bound on the carbon atom adjacent to the carbon atom substituted by R5 O-group, with a sulfonyl halide in the presence of a base to give a sulfonated compound(s) as shown in the following formulae (3) and/or (4) ##STR4## wherein R, R1, R2, R3, R4 and R5 are the same as defined above, and after the elimination of the protective group R5 of the sulfonated compound, cyclizing the compound by treating with a base.
The present invention is described in detail as shown in the following reaction scheme. ##STR5## wherein R, R2, R3, R4 and R5 are the same as defined above.
First, a diol compound (2) is reacted with a sulfonyl halide for example, an arylsulfonyl halide, such as benzenesulfonyl chloride, toluenesulfonyl chloride, etc. or C1 -C4 alkylsulfonyl halide, such as methanesulfonyl chloride, etc., in the presence of a base to give a monosulfonated compound (3) or a disulfonated compound (4) or a mixture of both compounds. As a base, an organic base, such as triethylamine, pyridine, etc., is used. This reaction is carried out in the absence of a solvent or in the presence of a solvent, for example, an ether, such as tetrahydrofuran, dioxane, t-butylmethyl ether, diethyl ether, etc., a chlorinated compound, such as methylene chloride, chloroform, dichloroethane, etc.; or an aromatic hydrocarbon, such as benzene, toluene, etc. The reaction temperature is 0°-100°C, preferably 10°-50°C This reaction proceeds in the absence of a catalyst, and the reaction is accelerated by using N,N-dimethylaminopyridine, etc., as a catalyst, and the yield is improved. When a mixture of a monosulfonated compound (3) and a disulfonated compound (4) is produced, the mixture can be separated by liquid column chromatography, etc. But the mixture may be used without separation in the next step.
Next, the elimination of the protective group R5 on the sulfonated compound (3) or (4) is carried out. When the protective group R5 is benzyl, allyl or benzyloxycarbonyl, the protective group is deprotected by being subjected to catalytic hydrogenation with palladium-carbon at room temperature in an organic solvent, such as methanol, ethanol, ethyl acetate, etc. When an o-nitrobenzyl is used as a protective group, the group is eliminated by radiation on it in an organic solvent, such as methanol, ethanol, etc. When the protective group R5 is t-butyldimethylsilyl, the protective group is removed by using a salt of a fluoro compound, such as sodium fluoride, potassium fluoride or tetrabutylammonium fluoride in an organic solvent, such as N,N-dimetylformamide, tetrahydrofuran, etc., or a mixture of the organic solvent and water. When the protective group R5 is methylenedioxy, isopropylidenedioxy, cyclohexylidenedioxy or diphenylmethylenedioxy, the protective group is eliminated under acidic conditions usually used in the deprotection of such a protective group.
A compound (5), a compound (6) or a mixture of them thus obtained is cyclized by treating it with a base to produce a desired 1,4-benzodioxane derivative (1A) (R1 ═H) and/or (1B) (R1 ═RSO2). Examples of the solvent are a dipolar aprotic solvent, such as N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, hexamethylphosphoramide, etc.; an ether, such as tetrahydrofuran, dioxane, t-butylmethyl ether, diethyl ether, etc.; a chlorinated compound, such as methylene chloride, chloroform, dichloroethane, etc.; an alcohol, such as methanol, ethanol, isopropanol, t-butanol, etc.; water, and so on.
Examples of the base are an alkali metal hydride, an alkali metal hydroxide, an alkaline earth metal hydroxide, an alkali metal carbonate, an alkaline earth metal carbonate, an alkali metal salt of C1 -C4 alkanol, or tri C1 -C4 alkylamine. Sodium hydride, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, triethylamine and ethyldiisopropylamine are illustrated. The amount of the base is 1-5 mol, preferably 1-3 mol per compound (5) or (6). The reaction temperature is -20°-80°C, preferably 0°-50° C. It is thought that on the cyclization of a compound (5), an epoxide is produced and then the epoxide reacts with a hydroxy on the benzene ring to give the cyclized compound. In this reaction there is a possibility to produce a 6 membered ring and a 7 membered ring, but the 6 membered ring is preferentially produced.
A 1,4-benzodioxane derivative (1A) (R1 ═H) thus prepared, is reacted with an arylsulfonyl halide, such as benzenesulfonyl chloride, toluenesulfonylchloride, etc.; or a C1 -C4 alkylsulfonyl halide, such as methanesulfonyl chloride, etc., in the presence of a base to produce a 1,4-benzodioxane derivative (1B) (R1 is RSO2, R is C1 -C4 alkyl, phenyl which may be substituted by C1 -C4 alkyl). When a mixture of a compound (5) and a compound (6) is cyclized, a mixture of a 1,4-benzodioxane derivative (1) wherein R1 is H, and a 1,4-benzodioxane derivative (1) wherein R1 is RSO2, is obtained, but this mixture is subjected to the next reaction with an arylsulfonyl halide or a C1 -C4 alkylsulfonyl halide in the same method as mentioned above to give only a compound wherein R1 is RSO2.
A diol compound (2), a starting material of the present invention, is synthesized according to the reaction scheme as mentioned below. ##STR6## wherein R2, R3, R4 and R5 are the same as defined above.
That is, a catechol derivative (7) is reacted with 3-chloro-1,2-propanediol (8) in the presence of a base in a solvent to produce a diol compound (2). The solvent is a dipolar aprotic solvent, such as N,N-dimethylformamide, dimethyl sulfoxide, sulfolane, hexamethylphosphoramide, etc.; an ether, such as tetrahhdrofuran, dioxane, t-butylmethyl ether, diethyl ether, etc.; a chlorinated compound, such as methylene chloride, chloroform, dichloroethane, etc.; an alcohol, such as methanol, ethanol, isopropanol, t-butanol, etc.; water, and so on.
Examples of the base are an alkali metal hydride, an alkali metal hydroxide, an alkaline earth metal hydroxide, an alkali metal carbonate, an alkaline earth metal carbonate, an alkali metal salt of C1 -C4 alkanol, or tri C1 -C4 alkylamine. Sodium hydride, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, sodium methoxide, sodium ethoxide, triethylamine and ethyldiisopropylamine are illustrated. Sodium hydride, sodium methoxide or sodium ethoxide is preferably used, and sodium hydride among them is more preferably used. The amount of the base is 1-4 mol, preferably 1.1-2.5 mol per compound (7). The reaction temperature is -20°-150°C, preferably 20°-100°C When the reaction temperature is too low, the reaction rate decreases and that is not practical. On the other hand, when the temperature is too high, a glycidol produced during the reaction may be polymerized and the yield is significantly reduced.
A diol compound (2), a starting material, used in the present invention, may be prepared by the known method, that is by reacting a catechol derivative (7) with glycidol. Glycidol is unstable and is readily polymerized, but 3-chloro-1,2-propanediol (8) is stable and not expensive and the method consisting of the use of this compound (8) as mentioned above, therefore, is beneficial in the industrial scale.
Also, by using an optically active diol compound (2), an optically active 1,4-benzodioxane derivative is prepared. Such an optically active diol compound (2) is prepared, for instance, by reacting a catechol derivative (7) with optically active 3-chloro-1,2-propanediol under the same conditions mentioned above. When 3-chloro-1,2-propanediol having high optical purity is used as a starting material, the racemization is not markedly occurred during the reaction and therefore, a 1,4-benzodioxane derivative is obtainable in the high optical purity. 3-Chloro-1,2-propanediol having the high optical purity (more than 98% ee), for example, is obtained by using the method described in Japanese patent publication No.73998/1992 or No.73999/1992 developed by the present applicant. According to the process of the present invention, a (S)-1,4-benzodioxane derivative is obtained from (R)-3-chloro-1,2-propanediol, and a (R) -1,4-benzodioxane derivative is obtained from (S)-3-chloro-1,2-propanediol.
The present invention is in detail explained in the following Examples, but the invention is not limited to the examples.
(i) Preparation of a Diol Compound
Sodium hydride (2.07 g, 0.05 mol in oil (60% w/w)) was washed with n-hexane, and anhydrous N,N-dimethylformamide (15 ml) was added to it. To the suspension was dropped 2-benzyloxyphenol (6 g, 0.03 mol) in anhydrous N,N-dimethylformamide (10 ml) under ice cooling in over a 10 minute period. After the emission of gas was over, to the solution was dropped monochlorohydrin (3.98 g, 0.036 mol) in anhydrous N,N-dimethylformamide (5 ml) under ice cooling. The solution was stirred for 3 hours at 60° C. After the reaction was completed, to the reaction mixture was added a saturated aqueous solution of ammonium chloride (500 ml) and the mixture was extracted with ethyl acetate, and the ethyl acetate phase was washed with saturated brine and water, dried over anhydrous magnesium sulfate and concentrated in vacuo to give a crude product as a pale yellow oil. The crude product was purified with column chromatography (silica gel, n-hexane/ethyl acetate (6:1)) to give 3-(2-benzyloxy)phenoxy-1,2-propanediol (7.88 g) as a colorless oil.
(ii) Preparation of a Compound (3) and a Compound (4)
The diol compound (7.88 g, 0.029 mol) obtained above (i) was dissolved in pyridine (10 ml) and to the solution was added p-toluenesulfonyl chloride (12.16 g, 0.064 mol) under ice cooling and then the mixture was stirred at room temperature for 12 hours. After the reaction was over, to the reaction mixture was added a 3% aqueous solution of hydrochloric acid (300 ml) and the mixture was extracted with ethyl acetate. The ethyl acetate phase was washed twice with water, dried over anhydrous magnesium sulfate and concentrated in vacuo to give 15.2 g of a mixture of a ditosylated compound and a monotosylated compound (ratio,6:1) as a pale yellow oil.
(iii) Preparation of a Compound (5) and a Compound (6)
In a mixture of ethanol (600 ml) and ethyl acetate (100 ml) was dissolved 15.2 g of a mixture of a ditosylated compound and a monosylated compound prepared above (ii) and the solution was subjected to hydrogenation under hydrogen in the presence of 10% palladium on carbon (1 g). After the reaction was finished, palladium/carbon was filtered off and the filtrate was concentrated in vacuo to give 12.9 g of a mixture of 1,2-ditosylated 3-(2-hydroxyphenoxy)-1,2-propanediol and 1-monotosylated 3-(2-hydroxyphenoxy)-1,2-propanediol.
(iv) Preparation of a 2,3-Dihydro-1,4-Benzodioxane Derivative
Sodium hydride (1.59 g, 0.04 mol in oil (60% w/w)) was washed with n-hexane and to it was added 10 ml of anhydrous N,N-dimethylformamide. To the suspension was added 12.9 g of a mixture of a 1,2-ditosylated compound and a 1-tosylated compound prepared above (iii) in anhydrous N,N-dimethylformamide (100 ml) under an atmosphere of nitrogen under ice cooling in over a 10 minute period and then the mixture was stirred for 3 hours at room temperature. To the solution was added a saturated aqueous solution of ammonium chloride and the solution was extracted with ethyl acetate. The ethyl acetate phase was washed with saturated brine and water, dried over anhydrous magnesium sulfate and concentrated in vacuo to give 7.5 g of a crude mixture of 2-tosyloxymethyl-1,4-benzodioxane and 2-hydroxymethyl-1,4-benzodioxane as a oil. The mixture might be purified with column chromatography (silica gel, n-hexane/ethyl acetate (3:2)), but the mixture was used for the next step without purification.
To 7.5 g of the mixture of 2-tosyloxymethyl-1,4-benzodioxane and 2-hydroxymethyl-1,4-benzodioxane in dichloromethane (15 ml) and pyridine (3.16 g, 0.04 mol) was added p-toluenesulfonyl chloride (0.76 g, 0.04 mol) under ice cooling and the mixture was stirred at room temperature for 12 hours. After the completion of the reaction, a 3% aqueous solution of hydrochloric acid (200 ml) was added to the reaction mixture and the reaction mixture was extracted with ethyl acetate and the ethyl acetate phase was washed twice with water, dried over anhydrous magnesium sulfate, and concentrated in vacuo to give a crude product as a oil. The crude product was purified with column chromatography (silica gel, n-hexane/ethyl acetate (3:1)) to give 7.89 g of 2-tosyloxymethyl-1,4-benzodioxane (yield 83% : based on 2-benzyloxyphenol).
By using 2-benzyloxy-3-methylphenol (6.43 g) instead of 2-benzyloxyphenol and by using optically active (R)-monochlorohydrin (optical purity:99.0% ee), according to the method of example 1 there was obtained (S)-2-tosyloxymethyl-8-methyl-1,4-benzodioxane (8.02 g, yield 80%). During the reaction the optical purity of (S)-2-hydroxymethyl-8-methyl-1,4-benzodioxane was 97.4% ee by the measurement with the chiral column OD (Daisel Chemical Industries Ltd.)
By using 2-benzyloxy-4,5-methylenedioxyphenol (7.33 g) instead of 2-benzyloxyphenol in the same method described in Example 1, there was obtained 2-tosyloxymethyl-6,7-methylenedioxy-1,4-benzodioxane (8.5 g, yield 78%).
By using 2-benzyloxy-3-methoxyphenol (6.91 g) instead of 2-benzyloxyphenol in the same method described in Example 1, there was obtained 2-tosyloxymethyl-8-methoxy-1,4-benzodioxane (8.51 g, yield 81%).
By using 2-benzyloxy-6-fluorophenol (6.55 g) instead of 2-benzyloxyphenol in the same method described in Example 1, there was obtained 2-tosyloxymethyl-5-fluoro-1,4-benzodioxane (7.04 g, yield 69%).
By using 2-benzyloxy-5-nitrophenol (7.36 g) instead of 2-benzyloxyphenol in the same method described in Example 1, there was obtained 2-tosyloxymethyl-6-nitro-1,4-benzodioxane (7.92 g, yield 72%).
By using 2-benzyloxy-5-ethoxycarbonylphenol (8.17 g) instead of 2-benzyloxyphenol in the same method described in Example 1, there was obtained 2-tosyloxymethyl-7-ethoxycarbonyl-1,4-benzodioxane (8.85 g, yield 75%).
On the occasion of the preparation of 2-tosyloxymethyl-8-hydroxy-1,4-benzodioxane, by using 4-hydroxy-2,2-dimethyl-1,3-benzo[d]dioxole (4.98 g) instead of 2-benzyloxyphenol, the objective compound was obtained, according to the method described in Example 1, provided that, intermediates (5) and (6) wherein R is p-CH3 C6 H4, R2 is 3-OH, R3 and R4 are H, were prepared as the following procedure.
A mixture (14.3 g) of a compound (3) and a compound (4) wherein R is p-CH3 C6 H4, R2 and R5 are -OC(CH3)2 -, R3 and R4 are hydrogen, was refluxed in 6N hydrochloric acid for 4 hours. After the reaction was over, to the mixture is added methylene chloride and the methylene chloride phase was washed with a saturated aqueous solution of sodium hydrogen carbonate and water, dried over anhydrous magnesium sulfate and concentrated in vacuo to give 11.8 g of a mixture of a compound (5) and a compound (6).
This mixture was treated in the same method described in Example 1 to give the objective compound (6.55 g, yield 65%).
According to the present invention, a 1,4-benzodioxane derivative is prepared in the high yield and by the convenient procedures in the industrial scale without the isolation of the intermediate produced during the reaction, by using a diol compound which is synthesized from a catechol derivative. Especially, it is economical to prepare a diol compound by reacting a catechol derivative with 3-chloro-1,2-propanediol. And in this reaction, by using an optically active 3-chloro-1,2-propanediol, a 1,4-benzodioxane of high optical purity is obtainable without marked racemizaion during the reaction.
Furukawa, Yoshiro, Kitaori, Kazuhiro, Takenaka, Keishi
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